Porous membranes are utilized in various fields such as a water treatment field including drinking water production, water purification treatment, and waste water treatment. In recent years, simplified manufacturing process is desired in addition to the membrane performance such as high fractionation performance or hydrophilicity.
As a porous membrane, a polymer membrane containing a hydrophobic matrix polymer such as polyvinylidene fluoride and an amphiphilic block copolymer has been proposed in Patent Document 1. However, the porous membrane described in Patent Document 1 has a bubble point diameter of about from 122 to 198 nm and thus the fractionation performance thereof cannot be said to be sufficient for an ultrafiltration application. In addition, the block copolymer used in Patent Document 1 is produced by a controlled radical polymerization method such as nitroxide-mediated polymerization (NMP), thus the monomer is required to be removed after the polymerization, and as a result, the porous membrane cannot be said to be cost-effective.